The present invention relates to a method for migrating from one storage system to another, and more particularly to a method for smoothly migrating data from one storage system to another without shutting down these systems.
Data migration techniques for moving data stored in one storage system to another storage system are important in running a computer system to which storage systems are connected. For example, when a new storage system is introduced, the data in the old storage system may need to be moved to the new storage system.
Further, data may be moved from a storage system under high load conditions to that under low load conditions while using these storage systems. Data migration may be carried out not only between storage systems but also between storage devices in a storage system.
U.S. Pat. No. 6,108,748 discloses a technique of migrating data from one storage system to another transparently to the host while maintaining access by the host. This technique connects the new storage system to which data is to be migrated between the host computer and the old storage system from which the data is to be migrated. The data to be migrated is moved from the old storage system to the new storage system while the new storage system is receiving read/write requests for the data from the host computer. When the new storage system has received a read/write request for data to be migrated which has not yet been migrated, the new storage system first issues a read request to the old storage system to migrate that data and then processes the read/write request after the data migration.